Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $75.90   13.276%   $85.9765   $85.98   $86.00   $86.00  
  Purchase #2 $175.53   5.544%   $185.2614   $185.26   $185.25   $185.30  
  Purchase #3 $231.64   3.469%   $239.6756   $239.68   $239.70   $239.70  
  Purchase #4 $80.64   9.477%   $88.2823   $88.28   $88.30   $88.30  
  Purchase #5 $209.98   11.689%   $234.5246   $234.52   $234.50   $234.50  
  Purchase #6 $200.37   6.599%   $213.5924   $213.59   $213.60   $213.60  
  Purchase #7 $49.28   3.794%   $51.1497   $51.15   $51.15   $51.10  
  7 purchase totals = $1,023.34       $1,098.4625   $1,098.46   $1,098.50   $1,098.50